1. Field of the Invention
The present invention relates to a stator for use in an electric rotating machine such as motor or generator and, more particularly, to a wire connection structure in distributed winding structure of coils being regularly wound.
2. Description of the Related Art
Generally a stator of an electric rotating machine includes a stator iron core, coils mounted onto the stator iron core, and insulators that are mounted onto slots and serve to insulate the coils from the stator iron core.
For example, one of conventional stator iron cores is a cylindrical member formed by laminating thin steel plates, and in which a plurality of slots extending in a direction of central axis are circumferentially disposed at a predetermined pitch so as to be open to the inner circumferential side. To facilitate mounting of coils, a stator iron core formed into a strip has been proposed, in which a gap of the slots is made larger than a line width of a coil conductor, thereby enabling to mount a conductor having a large line width on the stator iron core. In such a stator iron core, two ends of the strip-shaped stator iron core are brought in butt to be annular after having mounted the coils, and both ends are jointed by, e.g., welding.
As for the configuration of coils, a structure, in which coil ends of a conductor for use in coil are turned back to be wave-wound on the outside of an axial end face of the stator iron core, has been proposed. To efficiently use a space of slots, another structure has been also proposed, in which two sets of coils are mounted at intervals of a predetermined number of slots so that a conductor of a set of two lines runs in an inner layer and outer layer of a depth direction of the slots alternately, and these coils are distributed—wound into six phases (for example, see the Japanese Patent Publication (unexamined) No. 211584/2002 (on pages 5–8, FIGS. 2–6).
The number of turns of a coil has a great effect on performance of an electric rotating machine. Supposing that the number of turns is limited, a performance design appropriate for various uses cannot be done.
For example, in the case of employing an electric rotating machine in an AC generator of an automobile, taking notice of the relation between an output current of the generator and an engine speed of an engine proportional to the number of revolutions of a rotor, it is acknowledged that, in an electric generator of a larger number of turns of coil, an output current at low speed becomes lower while an output current at high speed becomes higher, as compared with an electric generator of a smaller number of turns of coil. It is certain that there are various needs in view of the balance in output current between at low speed and at high speed. But as the number of coils in a slot is specified and the number of turns of coil is an integer, thus resulting in a problem of occurring some cases not satisfying the above-mentioned needs.
As a solution to such a problem, a construction in which Δ-connection of an integral number of turns of coils and Y-connection of an integral number of turns of coils are combined has been proposed. In this construction, out of two sets of three-phase coils of integral turns, one set of three-phase coil is Δ-connected, and the other set of three-phase coil is connected to connection points of the Δ-connection. Thus, two sets of the three-phase coils are located at slot positions, which is in a state of being shifted by π/6 electrical angle to each other.
With this construction, even if the number of turns of two sets of three-phase coils is integers, the number of turns in the wire connection state of the Δ-connection and Y-connection can be the number of turns between integers (non-integral turn number) (for example, see the Japanese Patent Publication (unexamined) No, 247787/2002 (on pages 4–5, FIGS. 2–5).
However, in the construction of the mentioned Japanese Patent Publication (unexamined) No. 247787/2002, a problem exists in that two sets of three-phase coils are needed. Moreover, another problem exists in that since respective turn numbers of two sets of three-phase coils are set to be integers, the number of non-integral turns in the wire connection state of the Δ-connection and Y-connection cannot be obtained unlimitedly.